Method of producing high silicon steel articles



Patented Feb. 19, 1935 nm'rnon or PRODUCING HIGH SILICON STEEL ARTICLESGustav A. Reinhardt, Youngstown, Ohio, assignor to The Youngstown Sheetand Tube Company, Youngstown, Ohio, a corporation of Ohio No Drawing.Application February 15, 1932, Serial N0. 593,202

7 Claims. (Cl. 175-21) The present-invention relates to the manufacturefrom high silicon steel of articles especially adapted to be built toform a laminated body having a high degree of magnetic permeabilityaccompanied with relatively low hysteresis losses and thus suitable foruse in electrical apparatus such as transformers, motor and generatorarmatures and the like, the invention being more particularly directedto an improved method of 10 manufacturing the individual pieces orarticles preparatory to their being assembled to form the laminatedbody.

In the ordinary manufacture of articles or pieces of this character,steel having up to l to 5% silicon is usually employed, being hot rolledinto sheets or strips of about 28 to 29 U. S. standard gage, that is, toa thickness of about 0.0156" to-0.0141" from which the shapes or piecesare formed by stamping, but ithas heretofore been extremely diflicult,if not impossible, to satisfactorily produce the latter from this andlike materials for the reason that when the sheets or strips are hotrolled, annealing is thereafter reguired to produce the large grainstructure necessary to impart suitable magnetic and other propertiesthereto, but such annealing produces also an increased brittleness inthe sheets or strips which is highly inimical to the subsequent stampingor like operations by which the pieces 30 are individually formed.

If the hot rolling of silicon steel sheets is completed below thethermocritical range in accordance with the usual sheet rollingpractice, the

( material lacks the magnetic and other properties desired when theparts made therefrom'are to be used in electrical apparatus requiringhigh magnetic permeability so that, so far as I am aware, no method hasheretofore been devised for manufacturing high silicon steel articles ofthe 40 character described at a relatively low cost, without relativelylarge and extravagant losses from breakage in stamping or otherwise orwithout depriving the resultant articles of the magnetic and otherproperties sought for and substantially necessary to enable the articlesto be satisfactorily employed for their intended purpose.

On the other hand, it has been observed when rolling sheets or stripswith the use of severe cold rolling, that is, with about 75% coldreduction in thickness, such as results from rolling while under tensionon a backed up or cluster mill of the Coryell type, followed byannealing, a higher degree of ductility is produced than would resultwhen the same gage of sheet is rolled with moderate cold working in thecustomary manner as generally practiced in sheet mills, followed byannealing.

' A principal object of the present invention,

therefore, is to provide an improved method for of relatively highmagnetic permeability and subject to only relatively low hysteresislosses may be readilyand cheaply manufactured with a minimum number ofoperations and undue brittleness and hardness in the ultimate articlesavoided.

"Other objects, purposes and advantages of the invention willhereinafter more fully appear or will be understood from the followingdescription of a preferred manner of performing the invention in themanufacture of stamped shapes adapted to be built into transformercores, armature cores, and the like.

It will be understood that the material-usually supplied for manufactureinto the ultimate articles of the class described is in the form ofingots or bars such as are ordinarily termed sheet v bars or pairs inthe trade which may be made in any usual way from steel having a highsilicon content, for example, from l to 5%. In accordance with thepresent method these bars, after being heated to a suitable hot-rollingtemperature, are first progressively hot rolled in a suitable mill ormills to reduce them to sheets, desirably about 16 U. S.standard gage,i. e.,'about 0.0625" in thickness. The attenuation of the metal whichtakes place during this hot rolling results in a sheet having a grainstructure and electrical properties rendering it distinctly unsuitablefor electrical work of the character heretofore mentioned, but inaccordance with my method, the hot rolled sheets or strips are allowedto cool and, when cold, are subjected to great pressure such, forexample, as that which may be produced on a cluster mill havingrelatively large backing up rolls-providing support for working rolls ofcomparatively small diameter, or on a 4-high mill or the like preferablyprovided with rolls of the character just mentioned so as to secure alarge angle of bite in the metal while under tension,

to further reduce the thickness of the metal to- 28 or 29 U. S. standardgage while subjecting it to very severe cold. working which rearrangesthe grain structure and produces a sheet or strip of suitable thicknessand of suflicient ductility and malleability for relatively easystamping. The now relatively thin material is thereafter delivered to astamping press or other mechanism suitable for cutting it into thedesired shapes, for example, into small pieces the outlines of whichconform generally to the several transverse sections of the body to bemade of the shapes, whereby whena number of the latter are laid togetherwith their edges in superposed alignment, a laminated article for use asa transformercore, armature core or the like willemployed in electricalapparatus in such way as to serve as conductors of a magnetic field,this annealing also operating to relieve internal strains produced bythe stamping operation.

It will thus be understood that my improved method as hereinabovedescribed does not require any special machinery for its performance, aseach of the several steps may be effected. with the aid of apparatusordinarily found in many sheet and/or strip mills and other factories inwhich hot and cold rolling and stamping of steel plates, strips andsheets are performed. Moreover, my method, of producing articles of thecharacter to which the invention relates involves no greatercomplication than the methods heretofore employed for like purposes,while the desired properties are imparted to the resultant product to agreater degree and undesirable properties such as excessive brittlenesssubstantially eliminated.

It will furthermore be understood that while I have herein describedwith some particularity one manner of performing the method of myinvention with the aid of the apparatus to which specific reference hasbeen made, changes in andmodification of the specific operationsincident to the method may be made if desired and any suitable apparatusutilized in the practice of the invention, without departing from thespirit and scope thereof as defined in the appended claims.

Having thus described my invention, I claim and desire to protect byLetters Patent of the United States:

1. The method of producing steel articles having a high degree ofmagnetic permeability and not readily subject to material hysteresis,which comprises the steps of hot rolling a bar of high silicon steel tothereby form a relatively attenuated sheet or strip of substantialthickness, thereafter cold rolling said sheet or strip to substantiallydecrease its thickness, then cutting the arfrom a plurality ticlestherefrom, and finally annealing the articles to produce therein apredetermined grain structure.

2. The method .of producing articles of the character described whichcomprises the steps of hot rolling a body of high silicon steel, there-.

standard, thereafter cold rolling said reduced bar until its thicknessapproximates 29 gage U. S.

standard, then stamping the articles to shape therefrom, and finallyannealing the stamping: to produce a relatively large grain structuretherein.

4. The method of producing a metal article having a relatively largegrain structure and consequent high magnetic permeability, whichcomprises the steps of reducing by hot rolling to a sheet or strip ofpredetermined thickness a bar of high silicon steel, next subjecting therolled sheet or strip to severe cold working to further materiallyreduce its thickness to a predetermined point, then stamping from thematerial articles of the desired shape, and finally subjecting thestamped articles to an annealing treatment adapted to enlarge theirgrain structure to the desired point and also relieve internal strains.

5. In a method of producing thin steel articles of high magneticpermeability,.the steps of hot rolling a stefl shape containing arelatively large amount of s licon into a sheet or strip ofpredetermined thickness, and then cold working said sheet or strip toeffect a further and material reduction in its thickness and render thesheet or strip suitable for a subsequent stamping op- I eration.

6. In a method of producing thin steel articles of high,magneticlpermeability, the steps of hot rolling a steel shape containingfrom 4% to 5% of silicon into a sheet of approximately 16 gage U. S.standard thickness, and then subjecting the sheet while cold to severepressure to effect is further reduction to approximately 29 gage U. S.standard thickness.

'7. The method of producing high silicon thin steel articles whichcomprises the steps of hot rolling a steel shape having the desiredanalysis into a sheet or strip of predetermined thickness, then coldworking the sheet or strip to reduce its thickness to that desired inthe finished articles, stamping the articles from the cold worked metal,and finally enlarging the grain structure of the stamped articles toenhance their magnetic permeability.

GUSTAV A. REINHARDT.

